Calcium is an important component which forms human bones and tooth. It is further known that the substance is essential also in the cardiovascular and neurotransmission. Furthermore, it is well-known that collagen exists in almost all tissues including human bones, cartilages, tooth, skin, vessels and organs, and in other words, it is an essential component which is indispensable for organization of human body. However, due to decrease of the calcium and collagen for various reasons, so-called aging symptoms such as osteoporosis and hypometabolism become obvious.
Hydroxyapatite is a common designation for inorganic chemicals consisting mainly of calcium and phosphoric acids and expressed by a formula Ca10(PO4)6(OH)2. It is a main component of bones and tooth. Concerning a process for manufacturing, the hydroxyapatite the one using fish scale has been proposed. As a prior art document which describes the process for manufacturing the fish scale-derived hydroxyapatite, there is a disclosure in JP Laid-Open 2001-211895.
On the other hand, collagen belongs to proteins and is often extracted from collagen tissues of mammals like a cow and a pig. However, these mammals are always facing a risk of infection of pathogens such as prions which are eliminated with difficulties using ordinary sterilization and pasteurization methods, thus a manufacture of collagen from fish which are free from such fear. A fish skin is used in the manufacture of collagen from fish, a problem is raised that the collagen from the fish skin smells like fish and generates white turbidity leading to a low permeability. Therefore, several processes for manufacturing collagen from fish scale, wherein the processes can contribute to a solution for fish-like smells particular to fish, have been proposed. As prior art documents which describe the process for manufacturing collagen from the fish scale, there are disclosures in JP Laid-Open Patent Publications H05-155900, 2001-327599 and 2003-238598.
It is known that the hydroxyapatite as above described or the traditional calcium are, though poorly absorbed by a human body, biocompatible, and further, once absorbed by a human body, these substances can supplement these components that are deficient inside a human body. Starting from this common knowledge, the inventors have devotedly studied in order to facilitate a digestion and absorption by a human body, so that they have finally found out that, although calcium has conventionally been considered as showing a poor absorption, the collagen is assigned a scaffolding function by forming a composite from the hydroxyapatite and collagen, so that the hydroxyapatite absorbed on the collagen is well absorbed by a human body. Based on these findings, the inventors have then elaborated the present invention.